Revert "luci: Increase CQ experimental percentage to 80 from 60 for pie-arm64-rel"

This reverts commit f6120650.

Reason for revert: webview and weblayer test suites have a bad time today and causes the pending time spiking for Pie.
Will reland this CL once the issue is resolved.

Original change's description:
> luci: Increase CQ experimental percentage to 80 from 60 for pie-arm64-rel
>
> After the test suites adjustment in crrev.com/c/2427028, the device
> usage looks in a good shape and should be able to hold more traffc:
> http://shortn/_E2uBVeObl6
>
> Bug: 1111436
> Change-Id: I9bfb44a96feb2bc2d49ec8335afc73324711db5c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2429931
> Reviewed-by: Ben Pastene <bpastene@chromium.org>
> Commit-Queue: Haiyang Pan <hypan@google.com>
> Cr-Commit-Position: refs/heads/master@{#811298}

TBR=estaab@chromium.org,bpastene@chromium.org,hypan@google.com

Change-Id: I16bc0c24eaab0e2067c3554a9b3476d8acbbe6cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1111436
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437009Reviewed-by: Haiyang Pan <hypan@google.com>
Commit-Queue: Haiyang Pan <hypan@google.com>
Cr-Commit-Position: refs/heads/master@{#811382}

infra/config/generated/commit-queue.cfg

@@ -285,7 +285,7 @@ config_groups {
       }
       builders {
         name: "chromium/try/android-pie-arm64-rel"
-        experiment_percentage: 80
+        experiment_percentage: 60
         location_regexp: ".*"
         location_regexp_exclude: ".+/[+]/docs/.+"
         location_regexp_exclude: ".+/[+]/infra/config/.+"

infra/config/generated/cq-builders.md

@@ -351,7 +351,7 @@ as required builders.
   * Experiment percentage: 20
 
 * [android-pie-arm64-rel](https://ci.chromium.org/p/chromium/builders/try/android-pie-arm64-rel) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+android-pie-arm64-rel)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+android-pie-arm64-rel))
-  * Experiment percentage: 80
+  * Experiment percentage: 60
 
 * [fuchsia-compile-x64-dbg](https://ci.chromium.org/p/chromium/builders/try/fuchsia-compile-x64-dbg) ([definition](https://cs.chromium.org/search?q=package:%5Echromium$+file:/cq.star$+-file:/beta/+-file:/stable/+fuchsia-compile-x64-dbg)) ([matching builders](https://cs.chromium.org/search?q=+file:trybots.py+fuchsia-compile-x64-dbg))
   * Experiment percentage: 50

infra/config/subprojects/chromium/try.star

@@ -324,7 +324,7 @@ try_.chromium_android_builder(
     # TODO(crbug.com/1111436): Enable on CQ fully once the tests run fine.
     main_list_view = settings.main_list_view_name,
     tryjob = try_.job(
-        experiment_percentage = 80,
+        experiment_percentage = 60,
     ),
 )